Antibiotic derivatives of gentamicin c1a

ABSTRACT

DERIVATIVES OF GENTAMICIN C1A HAVE BEEN PREPARED WHICH POSSES SUBSTANTIALLY IMPROVED ANTIBACTERIAL ACTIVITY. AN EXAMPLE OF SUCH AN AGENT IS 1-(L-(-)-Y-AMINO-A-HYDROXYBUTYRYL)-GENTAMICIN C1A (IV,BB-K92).

United States Patent 3,796,699 ANTIBIOTIC DERIVATIVES 0F GENTAMICIN C Takayuki Naito, Susumu Nakagawa, and Yoshio Abe, Tokyo, Japan, assignors to Bristol-Myers Company, New York, N.Y. No Drawing. Filed Nov. 6, 1972, Ser. No. 303,741 Int. Cl. C07c 129/18 US. Cl. 260-210 AB 9 Claims ABSTRACT OF THE DISCLOSURE Derivatives of gentamicin C have been prepared which possess substantially improved antibacterial activity. An example of such an agent is 1- [L- )-'y-amino-a-hydroxybutyryl]-gentamicin C [IV, BB-K92].

BACKGROUND 'OF THE INVENTION (1) Field of the invention This invention relates to a semisynthetic l-substituted derivative of gentamicin C said compound being prepared by acylating the l-amino-function of gentamicin C with a 'y-amino-a-hydroxybutyryl moiety.

(2) Description of the prior art (A) Gentamicin (gentamycin) and the fermentation thereof is the subject matter of US. Pat. Nos. 3,091,572 which issued May 28, 1963 and 3,136,704 which issued June 9, 1964. The patents describe the fermentation of gentamicin complexes from Micromonospora purpurea, NNRL 2953 and Micromonospora echinospora, NNRL 2985. Variants thereof have also been deposited in the stock culture collection of the United States Department of Agriculture, Northern Utilization Research and Development Division, Peoria, 111. as M. echinospora var. ferruginea, NNRL 2995 and M. echinospora var. pallida, NNRL 2996.

(B) 'Gentamicin is further described in the Merck Index, 8th Edition, p. 485. The two major components, gentamicin C and C are described therein.

SUMMARY OF THE INVENTION The compound having the formula in which R is L-(-)-'y-amino-u-hydroxybutyryl; or a nontoxic pharmaceutically acceptable acid addition salt thereof is a valuable antibacterial agent.

This invention relates to a semi-synthetic derivative of gentamicin C said compound being known as 1- [L- -amino-u-hydroxybutyryl]-gentamicin C and having the formula in which R is L-()-' -amino-u-hydroxybutyryl; or a nontoxic pharmaceutically acceptable acid addition salt thereof.

For the purpose of this disclosure, the term nontoxic pharmaceutically acceptable acid addition salt shall mean a mono, di-, tri-, tetra, or penta-salt formed by the interaction of one molecule of Compound IV with 1-5 moles of a nontoxic, pharmaceutically acceptable acid. Included among these acids are acetic, hydrochloric, sulfuric, maleic, phosphoric, nitric, hydrobromic, ascorbic, malic and citric acid, and those other acids commonly used to make salts of amine containing pharmaceuticals.

Gentamicin C is fermented as a complex of three closely related components designated C C and C For the purpose of this application we are only concerned with gentamicin C the starting material of the compound of the instant invention which has the formula The compound of the present invention is prepared by the following diagrammatic scheme:

Gentamicin G Compound I] N-Hydroxysuccinimide ester amino-a-hydroxybutyric acid ca -na-ii-o-cu -c u A preferred embodiment of the present invention is the compound having the formula in which R is L-(--)-'y-amino'a-hydroxybutyryl or L- (-)-'y-benzyloxycarbonylamino-u-hydroxybutyryl and R is H or or a nontoxic pharmaceutically acceptable acid addition salt thereof.

Another preferred embodiment is the compound of Formula V in which R is C6H5CH:|O(HJ- and R is H.

A more preferred embodiment is the compound of Formula V in which R is and R is L-() y-benzyloxycarbonylamino-a-hydroxybutyryl.

A most preferred embodiment is the compound of Formula V in which R is H and R is L(-)-'y-amino-u-hydroxybutyryl; or a nontoxic pharmaceutically acceptable acid addition salt thereof.

Other most preferred embodiments are the sulfate, hy-

drochloride, acetate, maleate, citrate, ascorbate, nitrate or phosphate salts of Compound V.

A most preferred embodiment is the compound of Formula V wherein R is L-(-)'T-QmiHO-OL-hYdIOXYbUtYIYI and R is hydrogen; or the mono or disulfate salt thereof.

The objectives of the present invention have been achieved, by the provision according to the present invention of the process for the preparation of the compound having the formula in which R is L-()-'y-amino-whydroxybutyryl; or a nontoxic pharmaceutically acceptable acid addition salt thereof; which process comprises the consecutive steps of (A) Acylating gentamicin c with an acylating agent selected from the compounds having the formulas (or a carbodlimide thereof) or O &CH2CHr-C 0 11 (or a carbodiimide thereof) in which R and R are alike or difierent and each is H, F, Cl, Br, N0 OH, (lower)alkyl or (lower)alkoxy, X is chloro, bromo or iodo, or a functional equivalent as an acylating agent; in a ratio of one mole or less of acylating agent per mole of gentamicin C in a solvent, preferably selected from the group comprised of dimethylformamide, dimethylacetarnide, tetrahydrofuran, dioxane, 1,2-dimethoxyethane, methanol, ethanol, water, acetone, pyridine, N-(lower)alkylpiperidine, or mixtures thereof, but preferably 1:1 water-tetrahydofuran, at a temperature below 50 C. and preferably below 25 C., to produce the compound having the formula in which Y is a radical of the formula R GHa in which W is a radical selected from the group corm prising 5 C R HI N02 but preferably M is a radical from the group comprising I but preferably -0-N O O om-ah, mama. 5

(III) in which Y and W are as above; and

(C) removing the blocking groups Y and W from Compound III by methods commonly known in the art, and preferably when W and Y are radicals of the formula by hydrogenating Compound III with hydrogen in the presence of a metal catalyst, preferably selected from the group comprising palladium, platinum, Raney nickel, rhodium, ruthenium and nickel, but preferably palladium, and most preferably palladium on charcoal, in a waterwater miscible solvent system, preferably selected from the group comprising water and dioxane, tetrahydrofuran, ethyleneglycol dimethyl ether, propyleneglycol dimethyl ether, or the like, but preferably 1:1 waterdioxane, and preferably in the presence of a catalytic amount of glacial acetic acid to produce the compound of Formula IV.

:It should be apparent to those knowledgeable in the art that other agents can be used in the process above to acylate the amine functions of the intermediate compounds of the instant invention. This disclosure is meant to include all such acylating agents that produce labile amine blocking groups, said labile blocking groups commonly employed in the synthesis of peptides. The labile blocking groups must be readily removable by methods commonly known in the art. Examples of said labile blocking groups and their removal can be found in the review of A. Kapoor, J. Pharm. Sciences 59, pp. 1-27 (1970). Functional equivalents as acylating agent for primary amine groups would include corresponding carboxylic chlorides, bromides, acid anhydrides, including mixed anhydrides and particularly the mixed anhydrides prepared from stronger acids such as the lower aliphatic monoesters of carbonic acid, of alkyl and aryl sulfonic acids and of more hindered acids such as diphenylacetic acid. In addition, an acid azide or an active ester of thioester (e.g., with p-nitrophenol, 2,4-dinitrophenol, thiophenol, thioacetic acid) may be used or the free acid itself may be coupled with the gentamicin C derivative after first reacting said free acid with N,N'-dimethylchloroforminium chloride [cf. Great Britain 1,008,170 and Novak and Weichet, Experientia XXI/ 6, 360 1965)] or of alkynylamine reagent [cf. R. Buijile and H. G. Viehe, Angew, Chem, International Edition 3, (1964)], or of a ketenimine reagent [cf. C .L. Stevens and M. E. Munk, J. Amer. Chem. Soc. 80, 4065 (1958)] or of an isoxazolium salt reagent [cf. R. B. Woodward R. A. Olofson and H. Mayer, J. Amer. Chem. Soc., 83, 1010 (1961)]. Another equivalent of the acid chloride is a corresponding azolide, i.e., an amide of the corresponding acid whose amide nitrogen is a member of a quasiaromatic five membered ring containing at least two nitrogen atoms, i.e., imidazole, pyrazole, the triazoles, benzimidazole, benzotriazole and their substituted derivatives. As an example of the general method for the preparation of an azolide, N,N'-carbonyldiimidazole is reacted Compound W, l- [L-( -'y-amino-ot-hydroxybutyryl] gentamicin C possesses excellent antibacterial activity. Illustrated below is a table showing the minimal inhibitory concentrations (MICs) of gentamicin C Compound IV (BB-K92) and two other related monoand diacylated derivatives of gentamicin C against a variety of gram-positive and gram-negative bacteria as determined by the two-fold agar dilution method.

It can be seen that the process produced three different HABA-substituted gentamicin C derivatives, herein designated BB-K91, BB-K92 and BB-K93. BB-K92 was determined to be l-[L-(-)-'y-amino-a-hydroxybutyryl]- gentamicin C (Compound IV). The compound possessed activity comparable to that of gentamicin C and as such is useful as an antibiotic agent. BB-K91 is a monoacylated derivative whose acylation site has not been established. BB-K93 is a diacylated derivative Whose acylation sites have not been established.

It has been confirmed by thin layer chromatography (TLC) that all of the products, BB-K91 through BB- K93, regenerated gentamicin C and a-hydroxy-v-aminobutyric acid (HABA) by heating for one hour in 0.5 N sodium hydroxide solution. This fact, as Well as the presence of an amido carbonyl band in IR spectra, show that all of them are gentamicin C derivatives acylated with L-HABA.

The Compound IV is valuable as an antibacterial agent,

TABLE 1 [In vitro antimicrobial activity of gentamicin C derivatives] Gentamicin MIC (meg lml BB-K91 BB-K92 BB-K93 Ci.

E. coli NIHJ'. 1. 6 0. 8 0. 8 E. coli .Tuhl 1. 6 0.4 25 0.4 E. coli .Tuhl.-. 1. 6 0.8 25 0.8 E. coli .Tuhl KM-R 0. 8 0. 8 25 0.8 E. 6021' Juhl 1. 6 0.4 25 0. 4 E. coli Juhl KM-R 0.8 0. 1 6.3 0. 2 E. coli .Tuhl K-12 1.6 0.4 12. 5 0.4 E. coli K-12 KM-R 1 1. 6 0. 2 12. 5 0. 4 E. colt K-12 KM-R 3. 1 0. 4 25 0.4 E. coli W677 3. 1 0. 4 25 0. 4 E. coli .TR/W677- 6. 3 0.2 25 6. 3 K. pneumoniae D- 0. 2 0. 1 3. l 0. 1 K. pneumoniae Type 22 12. 5 0. 4 12. 5 Ser. marcescens 3. 1 1. 6 50 1.6 Pa. aeruginosa D-15 50 6.3 100 3. 1 .Ps. aerugi'nosa H9 D-113 KM-R 100 12.5 100 12. 5 Pa. aeruginosa H9 D-113 100 12. 5 100 6. 3 Pa. aerugi'nosa H9 Dll3 12. 5 0. 4 25 0.4 Pa. aeruginosa H9 D-113 100 12. 5 100 12. 5 P8. um H9 D413 A15194 100 6. 3 100 6. 3 P8. aeruginosa H9 D-1l3 GM-R A20717 100 50 100 100 Pa. aer'uginosa H9 D-1l3 GM-R A20718 100 50 100 100 Pa. aeruginosa H6 D-114 NM-R L 50 3. 1 100 6.3 Pr. zmlgaris 0.4 0.4 12. 5 0. 2 Fr. vulgaris 0. 8 0. 4 25 0. 2 Pr. mirabilis 3. 1 3. 1 50 0. 4 Pr. mirabilia 3. 1 1. 6 50 0. 4 Fr morganii 0.8 0. 8 50 0. 4 Fr morgzmu 1. 6 1. 6 100 0. 8 Pr rettgeri S. aureus Smith. 0.4 0.4 6.3 0.2 S aureus 2091 SM- 6. 3 1. 6 50 0. 8 S. aurcus KM-R h 1. 6 0. 8 50 0. 8 B. subtilis PCI-2l9 Mycob 607 3. 1 0.4 12. 5 0.8 Mycob. 607 KM-R l 100 50 100 100 Al /cob. 607 KM SM-R 100 50 100 100 Mycob. phlei 1. 6 0. 4 6. 3 0. 4 Mycob. nmae 3. l 0.4 12. 5 0.8

1 KM-R is kanamycin resistant. 2 SM-R is streptomycin resistant. B GM-R is gentamicin resistant. 4 NM-R is neomycin resistant.

Since gentam1c1n C has a primary ammo group atnutritional supplement in anlmal feeds, therapeutic agent tached to a methylene carbon at the 6'-position, the blocking of the amino group with a benzyloxycarbonyl group was carried out prior to the introduction of L- (')-y-amino-a-hydroxybutyric acid (HABA) onto the l-amino group of the deoxystreptamine moiety according to the following abbreviated scheme:

Gentemicin C 1 Cbz-NOS l 0 G50 column chromatography B B-K91 B B-K92 B B-K93 (monoacyl (the desired (diaeyl deriv.) l-acyl deriv.) deriv.)

temic bacterial infections when administered parenterally in the dosage range of about 250 mg. to about 3000 mg. per day in divided doses three or four times a day. Generally the compound is effective when administered at a dosage of about 5.0 to 7.5 mg./kg. of body weight every 12 hours.

Gentamicin C is a complex of at least three major components differing only in the R substituent found on the position of the dideoxy-sugar moiety of the gentamicin nucleus as shown below:

OH NR CH3 Ho Gentamln C1 CH-NH-CH:

Gentamin C1 CHNH1 Gentamicin C was obtained from the complex by the following procedure.

SEPARATION OF GENTAMICIN C COMPLEX Gentamicin C complex (0.10 g.), as the free base, was fractionated using a preparative counter current distribution (CCD) apparatus (100 m1. x 50 tubes) with a solvent system of OHCl -MeOH-17% aqueous NH OH (2: 1 :1) to give the fractions shown below.

Amount Identifi- Tube recovered, cation Fraction Nos. g. ('ILC 1.46 01 mainly. 0.72 01 z. 1.20 Cid-O 0.87 01.. mainly.

1 Cellulose thin-layer plate, solvent system: lower layer of CHCls-MeOH-17% NH4OH(2:2:1), Rt, gentamlcin Cr (0.69), C2 (0.39), C11 (0.23).

Dowex 1 X2 is a resin comprised of a polystyrene backbone to which is attached benzyltrimethylammonium chloride and 2% of added divinylbenzene as a crosslinking agent during polymerization of the polystyrene. It is supplied as beads.

EXAMPLES Example 1.-Preparation of L- -'y-benzyloxycarbonylamino-u-hydroxybutyrlc acid (VI) L-()-'y-amino-a-hydroxybutyric acid (7.4 g., 0.062 mole) was added to a solution of 5.2 g. (0.13 mole) of sodium hydroxide in 50 ml. of water. To the stirred solution was added dropwise at 05 C. over a period of 0.5 hour, 11.7 g. (0.068 mole) of carbobenzoxy chloride and the mixture was continued to stir for one hour at the same temperature. The reaction mixture was washed with 50 ml. of ether, adjusted to pH 2 with dilute hydrochloric acid and extracted with four 80-ml. portions of ether. The eflheral extracts were combined, washed with a small amount of saturated sodium chloride solution, dried with anhydrous sodium sulfate and filtered. The filtnate was evaporated in vacuo and the resulting residue was crystallized from benzene to give 11.6 g. (74%) of colorless plates; melting point 78.5-79.5 C., [a] -4.5 (c.-==2, CH OH,. Infrared (IR) [KBr]: IR(KBr)'y 1740, 1690 cm.- Nuclear Magnetic Resonance (NMR) (acetone-d 6 (in p.p.m. from TMS) 2.0 (2H, m.), 3.29 (2H,

10 d-d, J=6.7 and 12 Hz.), 4.16 (1H, d-d, 1:4.5 and 8 Hz.), 4.99 (2H, s.), 6.2 (2H, broad), 7.21 (5H, s).

Analysis.Calcd. for C H NO (percent): C, 56.91; H, 5.97; N, 5.53. Found (percent): C, 56.66; H, 5.97; N, 5.47.

Example 2.N-hydroxysuccinim-ide ester of L-()-'ybenzyloxycarbonylamino-a-hydroxybutyric acid (VII) A solution of 10.6 g. (0.042 mole) of VI and 4.8 g. (0.042 mole) of N-hydroxysuccinimide in 200 ml. of ethyl acetate was cooled to 0 C. and then 8.6 g. (0.042 mole) of dicyclohexylcarbodiimide was added. The mixture was kept overnight in a refrigerator. The dicyclohexylurea which separated was filtered 01f and the filtrate was concentrated to about 50 ml. under reduced pressure to give colorless crystals of VII which were collected by filtration; 6.4 g., M.P. 121-122.5 C. The filtrate was evaporated to dryness in vacuo and the crystalline residue was washed with 20 ml. of a benzene n-hexane mixture to give an additional amount of VII. The total yield was 13.4 g. (92%). [u] +1.5 (c.=2, CHCl IR (KBr) 70:0 1810, 1755, 1740, 1680 cm.- NMR (acetone-d 6 (in p.p.m. from TMS), 2.0 (2H, m.), 2.83 (2H, s.), 33.37 (2H, d-d, 1:65 and 12.5 Hz.), 4.56 (1H, m.), 4.99 (2H, s.), 6.3 (2H, broad), 723 (5H, s.).

Analysis.Cal'cd for C H N O (percent): C, 54.85; H, 5.18; N, 8.00. Found (percent): C, 54.79; 54.70; H, 5.21; 5.20; N, 8.14; 8.12.

Example 3.Prepara.ti0n of 1-[L-()v-amino-a-hydroxybutyryl1-gentamicin C (IV) To a solution of 379 mg. (0.84 mmole) of gent-amicin C in 20 ml. of water-THF (tetrahydrofuran) [1:1] was added 210 mg. 0.84 mmole) of N-benzyloxycarbonyloxysuccinimide and the mixture was stirred at room temperature for four hours. To the reaction mixture was added 87.3 mg. (0.84 mmole) of sodium carbonate and 297 mg. (0.84 mmole) of N-hydroxysuccinimide ester of L- -benzyloxycarbonylamino cc hydroxybutyric acid. After stirring for four hours the mixture was hydrogenated for 15 hours in the presence of 300 mg. of 10% palladium on charcoal. The catalyst was filtered off and the solution evaporated in vacuo to remove the organic solvent. The resulting aqueous concentrate was charged on a column of Amberlite CG-50 ion-exchanger (NH form, 25 ml), which was washed with ml. of water and eluated successively with 670 ml. of 0.1 N NH OH, 610 ml. of 0.2 N NH OH, 640 ml. of 0.3 N NH OH, 530 ml. of 0.5 N NH OH and 3-00 ml. of 1 N NH OH. The eluate was collected in 10-ml. fraction. The fractions were monitored by ninhydrin spot test, disc assay and TLC (thin layer chromatoraphy) on silica gel plate.

Fractions -195 were combined, evaporated in vacuo and lyophilized to produce 46 mg. of crude BB-K9l, 'WhlCh was rechromatographed on a column of CG-SO (NH 8 ml.) to yield 32 mg. of BB-K9l. Fractions 196- 220 were worked up as described above. Rechromatography with CG-SO produced gave 33 mg. of BB-K92 lgIBvkglg orkup of fractions 287-317 produced 10 mg. of

1 TLC: Silica gel plate, CHCla-MeOH-28% NH4OH-H2O (1:4:2:1).

Amberlite CG-SO is the trade name for the chromatographic grade of a weakly acidic cationic exchange resin of a carboxylic-polymethacrylic type.

1 G. W. Anderson et 0.1., J. Am. Chem. Soc., 86, 1839 (1964).

Example 4.-Preparation of L-( )-'y-amino-a-hydroxybutyric acid from ambutyrosin A or B or mixtures thereof Ambutyrosin A (5.0 gm.) [U.S. Pat. No. 3,541,078, issued Nov. 17, 1970] was refluxed with 160 ml. of 0.5 N sodium hydroxide for one hour. The hydrolysate was neutralized with 6 N HCl and chromatographed on a column of CG-50 (NH,+ type). The desired L-(-)-'y-amino-a-hydroxybutyric acid was isolated by developing the column with water and removing the water by freeze drying. The L-()-'y-amino-a-hydroxybutyric acid is characterized as a crystalline material having a M.P. of 212.5- 214.5 C. [Column 2, lines 31-38, U.S. Pat. No. 3,541,- 078].

Example 5.Preparation of L-(y-amino-u-hydroxybutyric acid from DL-a-hydroxy-y-phthalimidobutyric acid (A) Dehydroabietylammonium L-a-hydroxy-y-phthalimidobutyrate: To a solution of 25 g. (0.1 mole) of 2- hydroxy-y-phthalimidobutyric acid in 200 ml. of ethanol was added a solution of 29 g. (0.1 mole) of dehydroabietylamine in 130 ml. of ethanol. The solution was shaken vigorously for a minute and stood at room temperature for five hours during which time fine needles crystallized out. The crystals were collected by filtration, washed with 50 ml. of ethanol and air dried to obtain 30.1 g. (56%) of a diastereomer of the dehydroabiethylamine salt. M.P. 9394 C. [111 +15 (c. 2.5, MeOH). Recrystallization from 300 m1. of ethanol gave 23.2 g. (43%) of the pure product. M.P. 94-95 C. +l0.-8 (c. 2.5, MeOH). Further recrystallization did not change the melting point and the specific rotation.

Analysis.-Calcd. for C H N O -H O (percent): C, 69.54; H, 8.02; N, 5.07. Found (percent): C, 69.58; H, 0.08; N, 5.07.

(B) L-()-'ramino-u-hydroxybutyric acid: To a solution of 1.5 g. (0.014 mole) of sodium carbonate in 40 ml. of water were added 5.3 g. (0.01 mole) of dehydroabietylammonium L a hydroxy-y-phthalimidobutyrate and 60 ml. of ether. The mixture was shaken vigorously until all of the solid had dissolved. The ether layer was separated. The aqueous solution was washed twice with 20 ml. portions of ether and evaporated to 15 ml. under reduced pressure. To the concentrate was added 10 ml. ofconcentrated hydrochloric acid and the mixture was refluxed for ten hours. After cooling, separated phthalic acid was removed by filtration. The filtrate was evaporated under reduced pressure. The residue was dissolved in 10 ml. of water and the solution was evaporated to dryness. This operation was repeated twice to remove excess hydrochloric acid. The residual syrup was dissolved in 10 ml. of water and filtered to remove a small amount of insoluble phthalic acid. The filtrate was adsorbed on a column of IR-120 (H'*', 1 cm. x 35 cm.), the column was washed with 300 ml. of water and eluted with l N ammonium hydroxide solution. The eluate was collected in 15-ml. fraction. The ninhydrin positive fractions 10 to 16 were combined and evaporated under reduced pressure to give a syrup which crystallized gradually. The crystals were triturated with ethanol, filtered and dried in a vacuum desiccator to give 0.78 g. (66%) of L-()- 'y-amino-u-hydroxybutyric acid M.P. 206-207 C. [(11 -29 (c. 2.5, H The IR spectrum was identical with the authentic sample which was obtained from ambutyrosin. Amberlite IR-120 is the trade name for a high density nuclear sulfonic acid type cationic exchange resin supplied in either hydrogen or sodium form as beads 16-50 mesh.

Example '6.Preparation of the monosulfate salt of 1- [L-()-'y-amino-u-hydroxybutyryl]-gentamicin C One mole of 1-[L-()-'y-amino-a-hydroxybutyryl]- gentamicin C is dissolved in 1 to 3 liters of water. To

Y. Salto et al., Tetrahedron Letters, 1970, 4863.

the chilled and stirred solution is added one mole of sulfuric acid dissolved in 500 ml. of water. The mixture is allowed to stir for 30 minutes, following which cold ethanol is added to the mixture till precipitation occurs. The solids are collected by filtration and are determined to be the desired monosulfate.

Example 7.Preparation of the disulfate salt of l-[L- )-'y-amin0a-hydroxybutyryl] -gentamicin C One mole of 1-[L-()-'y-amino-a-hydroxybutyryl]- gentamicin C is dissolved in 1 to 3 liters of water. The solution is filtered to remove any undissolved solids. To the chilled and stirred solution is added two moles of sulfuric acid dissolved in ml. of water. The mixture is allowed to stir for 30 minutes, following which cold ethanol is added to the mixture until precipitation occurs. The solids are collected by filtration and are determined to be the desired disulfate salt.

We claim:

1. A compound having the formula cu -M41 in which R is L-()-'y-amino-a-hydroxybutyry1 or L- ()-'y-benzyloxycarbonylamino-a-hydroxybutyryl and R is H or oun-cm-o-iL,

or a nontoxic pharmaceutically acceptable acid addition salt thereof.

2. The compound of claim 1 wherein R is H and R is 0 O gHs-CHr-O- 3. The compound of claim 1 wherein R is L-()-'ybenzyloxycarbonylamino-u-hydroxybutyryl and R is UNITED STATES PATENTS 3,268,508 8/1966 Sugazawa et a1. 2'60210 K 3,647,779 3/1972 Schmitz 2-60-210 AB 3,651,042 3/1972 Marquez et al. 260-2l0 AB JOHNNIE R. BROWN, Primary Examiner US. Cl. X.R.

99-2 AB; 42418l 3 

